BAS Ozone Bulletin 11/99
The 1999 ozone hole filled rapidly in early December, however a
remnant area over central Antarctica, with ozone values below 270
DU, persisted until early February. The transition to winter
circulation is now taking place, with ozone amounts around
Antarctica increasing. Total ozone values at Halley just reached
300 DU in mid January and remained 10 - 15% below the normal,
with a slow decline from 280 DU in January to 250 DU in early
April. Stratospheric temperatures at Halley remained below the
normal until early April.
Note: Bulletin 10 was only posted on the
www page (http://www.antarctica.ac.uk/met/jds/ozone), and then
only in draft form. The final 1999 bulletin will be issued in
late May.
1. Data from the British Antarctic Survey (BAS) Halley station
(76-deg south, 27-deg west, on the Brunt ice shelf).
Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1999 October 8.
(0 indicates no data)
1999 August 21 - 2000 April 6
0 0 0 0 0 175 180 254
220 181 220
231 211 206 192 205 206 218 201 209 196
185 178 173 169 167 145 140 150 175 177
151 151 199 159 136 121 125 129 125 117
114 116 139 170 162 132 130 137 140 159
142 141 140 139 150 155 132 144 150 155
151 149 153 134 126 129 137 150 147 155 145
153 160 152 158 167 167 160 162 151 152
155 159 166 166 157 166 185 206 217 216
198 181 183 187 176 174 168 165 167 174
183 167 178 195 185 192 207 219 253 261
285 284 289 296 299 313 305 289 262 244
239 240 242 287 290 270 244 291 287 290 292
281 277 286 280 274 287 283 286 282 289
293 309 296 292 285 302 303 297 281 300
277 275 267 263 253 273 265 262 274 260 259
267 259 255 245 232 238 253 251 258 242
241 253 262 265 253 279 250 282 263 267
269 272 263 279 260 245 249 265 262
259 247 258 257 264 260 267 273 265 249
265 265 257 230 240 228 222 233 229 258
260 276 253 253 247 250 223 230 229 230 259
252 250 248 254 265 260
Halley provisional monthly mean total
ozone (DU)
Period Aug Sep Oct Nov Dec Jan
Feb Mar Apr Year
1999/00 205 172 143 172 254 281 258 250
1998/99 221 162 140 183 255 272 259 254 267 224
1997/98 218 171 141 210 286 267 262 264 261 231
1996/97 173 155 148 181 260 278 265 247 243 217
1995/96 218 160 130 164 252 261 249 246 226 212
1957-72 295 285 300 355 350 320 300 295 285 310
Note that August and April do not have
observations on every day, and that the routine measurement
season is now longer than it was in 1957 - 72. Measurements made
at the start of the season are of lower accuracy than in mid
summer due to the low solar elevation or use of moonlight. Gif
images showing the data are available on the BAS ozone web-page.
2. Data from the British Antarctic Survey (BAS) Rothera
station (68-deg south, 68-deg west on Adelaide Island).
1999 July 1 - 2000 April 10
270 277 293 278
293 324 304 294 301 311
298 294 294 293 298 273 247 219 0 211
231 276 279 277 243 224 238 244 265 273 283
299 313 281 270 267 290 0 258 260 260
210 228 239 256 249 243 200 232 262 239
225 222 219 224 241 214 210 210 225 219 223
186 175 0 165 164 194 183 162 158 164
154 143 162 160 184 149 148 163 162 162
159 173 161 166 130 129 119 116 114 0
150 175 192 207 157 274 292 280 279 239
155 151 145 136 126 110 124 124 145 155
151 148 138 0 166 178 172 156 154 164 207
227 204 254 313 320 276 259 236 165 0
188 187 172 193 217 242 282 288 231 191
190 250 289 282 217 162 164 173 220 262
257 198 168 178 240 302 319 322 326 329
327 324 315 313 302 0 0 0 264 287
306 302 310 309 292 296 306 302 299 308 304
285 275 285 298 305 306 304 302 301 303 257 250 255 265 272 278 275 274 268 266 273 289 294 289 291 289 278 0 289 275 278 276 286 274 269 273 276 270 262 259 255 253 254 243 0 0 0 0 0 0 0
0 0 0 0 0 0 0 253
265 278 282 271 275 284 286 286 280 282
282 269 257 263 236 247 267 265 264 256
256 0 0 275 275 284 259 235 227 242 231
246 280 285 306 303 284 325 320 320 298
Rothera provisional monthly
mean total ozone (DU)
Period Jul Aug
Sep Oct Nov Dec Jan Feb Mar Apr May Jun
1999/00 274 243 157 175 229 289 282 265 265
1998/99 288 239 159 166 252 264 270 279 267 277 300 287
1997/98 270 280 267 263
3. Data from the Ukrainian Antarctic Research Centre Vernadsky station (65-deg south, 64-deg west on the coast of the Antarctic Peninsula, formerly the BAS Faraday station).
1999 August 1 - 2000 April 5
296 319 275 275 282 288 262 253 254 265
229 215 230 268 258 264 219 234 232 226
226 244 226 236 240 206 215 231 261 235 252
219 191 177 186 174 237 224 194 170 182
201 196 174 183 233 199 171 222 208 181
199 215 181 242 161 173 159 142 146 138
145 183 208 250 164 249 309 301 269 280
196 195 187 177 163 145 145 152 182 204
181 180 187 165 178 194 219 206 197 232 229
281 259 261 334 347 308 323 334 252 259
224 275 281 259 328 329 343 347 274 229
206 273 334 343 309 189 213 206 252 307
335 252 209 172 195 289 321 328 331 325
320 315 312 331 311 315 294 284 279 282
298 304 321 317 303 308 317 312 299 312 304
293 310 285 294 286 306 308 316 311 310
292 272 261 281 276 286 293 294 293 276
281 315 311 279 313 292 290 284 292 286 280
287 279 271 285 296 302 297 283 276 263
269 293 282 277 257 272 261 283 279 294
290 265 252 266 243 218 232 242 259
285 287 266 262 283 278 287 284 287 260
258 268 275 251 233 267 254 241 254 262
268 250 270 278 288 268 239 235 243 221 217
296 310 291 320 283
Vernadsky provisional monthly
mean total ozone (DU)
Period Aug Sep Oct Nov
Dec Jan Feb Mar Apr Year
1999/00 249 189 202 283 297 292 271 262
1998/99 241 200 218 305 278 288 289 273 279 263
1997/98 261 251 235 240 297 281 266 280 281 266
1996/97 208 203 265 225 272 307 281 277 283 258
1995/96 240 199 252 230 296 284 285 276 264 258
1957-72 310 330 345 370 345 320 300 295 310 325
4. Information from other sources.
TOVS satellite images from the US NCEP/NWS/NOAA Climate
Prediction Center and EP/TOMS images from the US NASA/GSFC show
the formation of the ozone hole during August and September and
its rapid filling in early December. The margins of the hole
briefly crossed the southernmost tip of South America and the
Falkland Islands over November 21 to 22. A remnant area over
central Antarctica, with ozone values below 270 DU, persisted
from late December into early February. The transition to winter
circulation is now occurring. A broad collar with ozone values
generally above 300 DU surrounds Antarctica, but there are small
areas with values below 250 DU in south temperate latitudes. NOAA
analyses show that the 50 hPa temperature is dropping in the
unlit area of the polar cap, but is generally close to the
normal.
An interesting low ozone event in the Northern Hemisphere occurred around November 30th. Nacreous clouds were widely seen over Scotland and very low ozone values measured over the North Sea. These events were associated with unusually low stratospheric temperatures, with chemical depletion playing a minor part in the low ozone values. A further display of nacreous clouds was seen over the UK on January 29. NOAA analyses show that the Arctic 50 hPa temperature was below the normal from early December, reaching an extreme of -75 deg C in early January. Since then it has been rising, though remaining below the normal. Locally, conditions have been suitable for Type I PSC formation since mid December. At higher levels the temperature is close to the normal. Results from the THESEO 2000/SOLVE campaign show that local ozone losses of over 60% occurred near 18km in March, with total column depletions of 15 - 30%.
Further information is available on the BAS ozone web page, which
contains earlier bulletins, data, graphs and general ozone
information. The url is:
http://www.antarctica.ac.uk/met/jds/ozone
Note that all ozone values in this bulletin are preliminary and
are subject to revision from time to time when the instrument
constants are re-evaluated. Final data will be archived with
WOUDC, Toronto in due course, but preliminary data back to 1973
are available from BAS on request. All Dobson ozone data are
reduced to the Bass-Paur scale as recommended by the WMO. The
reference period used for the normals is 1957 - 1972. If you use
or pass on data in this bulletin please make acknowledgement to J
D Shanklin, British Antarctic Survey.